Effect of various doses of naloxone on circulating corticosterone levels in the rat

Abstract

The effect of three different doses of naloxone (2.5, 5 and 10 mg/kg w.i.p.), on the corticosterone levels has been studied in the Wistar male rat model, at 9 a.m.and 5 p.m.The 5 mg/kg w.dose, induces a significant increase on the p.m.values, while the 10 mg/kg w.dose determines highly significant increases on the a.m.and p.m.values, referred to its controls the p.m.ones being percentually higher.The putative role of endogenous opiates, given the naloxone specific antagonism in the activity of the hypothalamic-pituitary-adrenal axes is discussed, while the changes observed after naloxone injection are analyzed to see whether they are provoked by a direct effect of the drug on the adrenal gland or are mediated by a central mechanism.